Features in optional ROMs are listed as Option. Features in HP mag card or tape Application Pacs are listed as +. Other software is not included. 


Display and Keyboard  HP15C  HP42S 
Display type  LCD  LCD 
Display format  1 Line  2 Line 
FIXed number format  Yes  Yes 
SCIentific number format  Yes  Yes 
ENGineering number format  Yes  Yes 
STanDard / ALL number format    Yes 
Alpha messages and prompts    Yes 
Softkeys labeled by mag. card or overlay     
Softkeys labeled by display menus    Yes 
Softkeys with neither labeling system  Yes   
Status annunciators  Yes  Yes 
Redefinable keyboard    Yes 
Logic  HP15C  HP42S 
Logic system  RPN  RPN 
Stack levels  4  4 
Last x  Yes  Yes 
Undo     
Precedence     
Parentheses     
Storage Addition (STO +)  Yes  Yes 
Storage Arithmetic (STO +, −, ×, ÷)  Yes  Yes 
Storage Exponentiation (STO ^)     
Recall Arithmetic  Yes  Yes 
Named variables    Yes* 
Multiple data types    Yes* 
Directories     
Math  HP15C  HP42S 
+, −, ×, ÷  Yes  Yes 
1/x  Yes  Yes 
√  Yes  Yes 
x^{2}  Yes  Yes 
LOG x  Yes  Yes 
10^{x}  Yes  Yes 
LN x  Yes  Yes 
e^{x}  Yes  Yes 
y^{x}  Yes  Yes 
π  Yes  Yes 
%  Yes  Yes 
% change  Yes  Yes 
INTeger truncation and ABSolute value  Yes  Yes 
Trigonometric functions (SIN, COS etc.)  Yes  Yes 
Hyperbolic trig. (SINH, COSH etc.)  Yes  Yes 
# of trig. modes (degrees, radians, grads)  3  3 
Advanced Math  HP15C  HP42S 
Solver / root finder  Yes  Yes 
Numeric integration  Yes  Yes 
Complex numbers  Yes  Yes 
Matrix operations  Yes  Yes 
Matrix writer     
Equation writer     
Symbolic operations     
Fractions     
Plotting and graphics (display)    Yes 
Plotting and graphics (printer / plotter)    Option 
Statistical  HP15C  HP42S 
Mean, standard deviation (# of variables)  2  2 
Σ of n, x, x^{2}  Yes  Yes 
Σ of n, x, x^{2}, y  Yes  Yes 
Σ of n, x, x^{2}, y, xy  Yes  Yes 
Σ of n, x, x^{2}, y, y^{2}, xy  Yes  Yes* 
Σ of lists     
Random number generator  Yes  Yes 
Linear regression, estimate  Yes  Yes 
Curve fitting    Yes 
Correlation coefficient  Yes  Yes 
Normal distribution     
Factorial  Yes  Yes 
Gamma  Yes  Yes 
Combinations and permutations  Yes  Yes 
Scientific and Time  HP15C  HP42S 
Polar / rectangular conversions  Yes  Yes 
Base conversions (2, 8, 10, 16)    Yes 
Arithmetic in bases 2, 8 and 16    Yes 
Bit operations (AND, OR, XOR, ...)    Yes 
Selectable word size (164 bits)     
Selectable complement mode (1's, 2's, unsigned)     
Decimal hrs / hrs.min.sec. conversions  Yes  Yes 
Hrs.min.sec arithmetic    Yes 
Time of day clock     
Timer     
Dynamic calculations (timer × rate)     
Alarms     
Unit Conversions  HP15C  HP42S 
Centimeters / inches     
Millimeters / inches     
Meters / feet     
Kilograms / pounds (mass)     
Newtons / pounds (force)     
British thermal units / joules     
Liters / gallons     
° Celsius / ° Fahrenheit     
Other     
Userdefined units     
Time Value of Money  HP15C  HP42S 
Number of payments (n)     
Interest rate (i)     
Present Value (PV)     
Payment (PMT)     
Future Value (FV)     
Cash Flow Analysis  HP15C  HP42S 
Net present value (NPV)     
Internal rate of return (IRR)     
Amortization  HP15C  HP42S 
Accumulated Interest (ACC INT)     
Balance (BAL)     
Depreciation  HP15C  HP42S 
Straight line (SL)     
Sum of the years digits (SOYD)     
Declining balance (DB)     
Bonds and calendar functions  HP15C  HP42S 
Bond price     
Bond yield     
Date arithmetic / calendar functions     
Memory and Programming  HP15C  HP42S 
Programming language(s)  RPN  RPN 
RAM / Max # of variables or addressable registers  67  7200 bytes / 895 registers 
Max # of program steps  448*  7200* 
RAM / Max vars or regs with full optional RAM     
Max # of prog steps with full optional RAM     
Merged program steps  Yes  Yes 
Manual register / program memory allocation  Yes  Yes 
Automatic register / program memory allocation     
Overlapped register and program memory     
Continuous memory  Yes  Yes 
Flags  10  100 
Conditional tests  12  12 
Subroutine levels  7  8 
Indexed looping (increment by +/ 1, end at 0)  Yes  Yes 
Indexed looping (choice of increment and end)  Yes  Yes 
Multiple index / loop registers  Loop only  Yes 
Line number addressing  Via I*   
Branching by relative line number     
Global program label addressing  Yes  Yes 
Local program label addressing    Yes 
Indirect / computed addressing and control  Yes  Yes 
Multiple indirection registers    Yes 
Pause  Yes  Yes 
Alpha messages and prompts in programs    Yes 
Alpha program listings    Yes 
Alpha string manipulation    Yes 
Program step insert / delete  Yes  Yes 
I/O and Expansion Features  HP15C  HP42S 
ROM modules     
RAM modules or expansion option     
General expansion slots / connector     
Magnetic card reader/writer     
Tape drive     
Disk drive     
Upgradeable firmware     
Optical wand     
Serial port     
Infrared input     
Infrared output    Yes 
Printer    Option 
Networking     
Other     
General  HP15C  HP42S 
Sounds    Yes 
Self test  Yes  Yes 
Hard case (in addition to soft case)     
Additional Features     
Batteries  3 SR44  3 SR 44 
Length (inches)  5.1"  5.85" 
Width  3.1"  3.15" 
Height  0.6"  0.6" 
Weight (oz or lbs)  4 oz  5 oz 
Year of introduction  1982  1988 
Features in optional ROMs are listed as Option. Features in HP mag card or tape Application Pacs are listed as +. Other software is not included. Unlim means limited only by available memory. 
HP15C notes:

HP42S notes:

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